The invention relates to a portable lighting device comprising at least one light-emitting diode for emitting a light beam, a fixing and connecting element of said diode, and means for adjusting the light beam.
A light-emitting diode LED comprises in conventional manner a semi-conducting component in conjunction with a reflector inside an enclosure made of transparent plastic material, for example epoxide resin-based. The front part of the molded enclosure forms an internal lens or magnifying glass through which the light ray produced by the light-emitting diode passes when the latter has been connected to a power supply source. The visualization angle emitted by the diode depends on the shape of the reflector and on the internal distance between the component and the lens. This visualization angle is constant for a LED type diode, for example 20°, and concentrates most of the useful light flux.
To make the intensity of the light flux emitted by a LED diode vary, it is conventional to supply it by means of an adjustable current electronic circuit, for example a DC-DC converter, or a microcontroller connected to a disposable or rechargeable battery. This adjustment of the supply current causes a variation of the lighting power, but does not act on the radiation of the useful light flux. A conventional reflector of an incandescent lamp does not enable the visualization angle of a LED diode to be varied either, as it acts in a zone where the lamp emits very little light.
The document U.S. Pat. No. 6,474,837 concerns a lighting lamp with light-emitting diodes, comprising a rotating plate in the form of a diaphragm drilled with holes and equipped with lenses placed facing the holes.
The document WO 01/57,431 describes a lighting device composed of a LED diode in front of which there is permanently arranged a lens movable in translation to modify the relative distance with respect to the diode.